In conventional clapper type dot printer heads, a plurality of electromagnets are arranged in circular fashion about the central axis of the printer head. The same number of clappers are provided as electromagnets, the free end of the clapper engaging the input end of the printing wires, the other end of the clapper being its fulcrum. A turning force imparted to the clapper about its fulcrum is imparted to the printing wire by attracting the clapper or an attraction piece fixed thereon by the electromagnet. The printing wires engaged by the free end of the clappers are thrust outwardly in a printing direction.
Previously, one coil spring was used for each clapper to exert a biasing force thereon for returning it to its original standby position. Consequently, there were a large number of individual components and during assembly of the printer head, it was necessary to position each spring and clapper properly at its fulcrum and provide means for regulating the displacement of the clapper so as to maintain each clapper in an engaged position with the input end of each printing wire. For these reasons, the conventional printer heads included a large number of components, involved a complex construction providing great difficulties in assemblying the printer head. In addition, a large energy loss occurred due to friction between these various components. Accordingly, it is desirable to provide a wire type dot printer head including a plurality of clappers of simplified construction which would bias the clappers to their standby position and avoid the assembly problems noted above with respect to positioning the clappers and overcome the problems encountered in conventional dot printer heads.